Low thermal expansion articles

Abstract

Compositions, and articles having low thermal expansion suitable for high temperature applications, such as automotive exhaust treatment and method of manufacturing such articles are disclosed.

1. A ceramic article exhibiting a thermal expansion of 0.3×10 −7 /° C. or less over a temperature ranging from 25° C. to 800° C., comprising a composition having a needle-like morphology and comprising x(A)+y(Z 2 O 5 ), where x and y are mole fractions of each component such that x+y=1, wherein:
 a. A is R′O 2 , wherein:
 R′ is selected from the group consisting of titanium (Ti) and zirconium (Zr), and 0.15≦x≦0.80 when R′ is Ti, and 0.05≦x≦0.76 when R′ is Zr; and 
 
 b. Z is niobium (Nb), wherein:
 0.2≦y≦0.95 for Nb 2 O 5 . 
 
 
     
     
       2. The ceramic article of  claim 1  wherein for R′O 2 , when R′ is Ti then 0.15≦x≦0.30. 
     
     
       3. The ceramic article of  claim 1  wherein for R′O 2 , when R′ is Zr then 0.10≦x≦0.30. 
     
     
       4. The ceramic article of  claim 1  wherein 0.45≦y≦0.90 for Nb 2 O 5 . 
     
     
       5. The ceramic article of  claim 1  wherein the composition further includes an additives selected from the group consisting of alkali metal oxides and rare earth oxides. 
     
     
       6. The ceramic article of  claim 5  wherein the alkali metal oxides are selected from the group consisting of Li 2 O, Na 2 O, K 2 O, Rb 2 O, and Cs 2 O. 
     
     
       7. The ceramic article of  claim 5  wherein the rare earth oxides are selected from the group consisting of Y 2 O 3 , and La 2 O 3 . 
     
     
       8. A method of manufacturing a ceramic article exhibiting a low thermal expansion of 0.3×10 −7 /° C. or less over a temperature ranging from 25° C. to 800° C., and being suitable for high temperature applications comprising:
 a. formulating a batch of raw materials selected from the group consisting of oxides, carbonates, nitrates, fluorides, phosphoric acid, and boric acid; 
 b. mixing the raw material batch with processing aids selected from the group consisting of plasticizers, lubricants, and binders to form a homogenous and plasticized mixture; 
 c. shaping the homogenous and plasticized mixture by extrusion to form a green body; 
 d. heating the green body to a top temperature of 1200° C. to 1650° C. for a period of 1-24 hours to form a ceramic having a composition having a needle-like morphology and comprising x(A)+y(Z 2 O 5 ), where x and y are mole fractions of each component such that x+y=1, wherein:
 i. A is R′O 2 , wherein
 R′ is selected from the group consisting of titanium (Ti) and zirconium (Zr), and 0.15≦x≦0.80 when
 R is Ti, and 0.05≦x≦0.76 when R is Zr; and 
 
 
 ii. Z is niobium (Nb), wherein:
 0.2≦y≦0.95 for Nb 2 O 5 . 
 
 
 
     
     
       9. A method of manufacturing a ceramic article exhibiting a low thermal expansion 0.3×10 −7 /° C. or less over a temperature ranging from 25° C. to 800° C., and being suitable for high temperature applications comprising:
 a. formulating a batch of raw materials including phosphoric acid and one or more selected from the group consisting of oxides, carbonates, nitrates, fluorides and boric acid; 
 b. mixing the raw material batch with processing aids selected from the group consisting of plasticizers, lubricants, and binders to form a homogenous and plasticized mixture; 
 c. shaping the homogenous and plasticized mixture by extrusion to form a green body; 
 d. heating the green body to a top temperature of 300° C. to 1450° C. for a period of 1-24 hours to form a ceramic having a composition having a needle-like morphology and comprising x(A)+y(Z 2 O 5 ), where x and y are mole fractions of each component such that x+y=1, wherein:
 i. A is R′O 2 , wherein:
 1. for R′O 2 , R′ is selected from the group consisting of titanium (Ti) and zirconium (Zr), and 0.15≦x≦0.80 when R is Ti, and 0.05≦x≦0.76 when R is Zr; 
 
 ii. Z is niobium (Nb), wherein:
 0.2≦y≦0.95 for Nb 2 O 5 . 
 
 
 
     
     
       10. The method of  claim 9  wherein the green body is heated to a temperature of 300° C. to 600° C. for a period of 1-24 hours. 
     
     
       11. A ceramic article exhibiting a thermal expansion of 0.3×10 −7 /° C. or less over a temperature ranging from 25° C. to 800° C., having a composition comprising x(A)+y(Z 2 O 5 ), where x and y are mole fractions of each component such that x+y=1, wherein:
 a. A is R′O 2 , wherein:
 R′ is selected from the group consisting of titanium (Ti) and zirconium (Zr), and 0.15≦x≦0.80 when R′ is Ti, and 0.05≦x≦0.76 when R′ is Zr; 
 
 b. Z is niobium (Nb), wherein:
 0.2≦y≦0.95 for Nb 2 O 5 ; and 
 
 
       wherein the composition further includes an additive selected from the group consisting of alkali metal oxides and rare earth oxides. 
     
     
       12. The ceramic article of  claim 11 , wherein for R′O 2 , when R′ is Ti then 0.15≦x≦0.30. 
     
     
       13. The ceramic article of  claim 11 , wherein for R′O 2 , when R′ is Zr then 0.10≦x≦0.30. 
     
     
       14. The ceramic article of  claim 1  wherein 0.45≦y≦0.90 for Nb 2 O 5 . 
     
     
       15. The ceramic article of  claim 5  wherein the alkali metal oxides are selected from the group consisting of Li 2 O, Na 2 O, K 2 O, Rb 2 O, and Cs 2 O. 
     
     
       16. The ceramic article of  claim 5  wherein the rare earth oxides are selected from the group consisting of Y 2 O 3 , and La 2 O 3 . 
     
     
       17. A method of manufacturing a ceramic article exhibiting a low thermal expansion 0.3×10 −7 /° C. or less over a temperature ranging from 25° C. to 800° C., and being suitable for high temperature applications comprising:
 a. formulating a batch of raw materials including phosphoric acid and one or more selected from the group consisting of oxides, carbonates, nitrates, fluorides and boric acid; 
 b. mixing the raw material batch with processing aids selected from the group consisting of plasticizers, lubricants, and binders to form a homogenous and plasticized mixture; 
 c. shaping the homogenous and plasticized mixture by extrusion to form a green body; 
 d. heating the green body to a top temperature of 300° C. to 1650° C. for a period of 1-24 hours to form a ceramic having a composition comprising x(A)+y(Z 2 O 5 ), where x and y are mole fractions of each component such that x+y=1, wherein:
 i. A is R′O 2 , wherein:
 1. for R′O 2 , R′ is selected from the group consisting of titanium (Ti) and zirconium (Zr), and 0.15≦x≦0.80 when R is Ti, and 0.05≦x≦0.76 when R is Zr; 
 
 ii. Z is niobium (Nb), wherein:
 0.2≦y≦0.95 for Nb 2 O 5 ; 
 
 
 
       wherein the composition further includes an additive selected from the group consisting of alkali metal oxides and rare earth oxides. 
     
     
       18. The method of  claim 17  wherein the green body is heated to a temperature of 300° C. to 600° C. for a period of 1-24 hours.